The figure shows a rectangle inscribed in a circle. The side AB measures 28 em and side BC measures 21 cm. A black ant starts travelling from point A along the circumference of circle at 22 cm/minute. She will complete 7 rounds in x minutes.
x | 30 |
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Solution
By Pythagoras theorem, diameter AC = 35 cm.
∴ Circumference circle = \(\frac{22}{7}\) × 35 = 110 cm.
∴ Black ant would take \(\frac{110}{22}\) = 5 minutes to complete one round and reach A again.
She will complete 7 rounds in 7 × 5 = 35 min.
∴ x = 35 min
Seed of boat in still water in kmph | 12 |
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Solution
Let speed of boat in still water = x kmph.
∴ Upstream speed = x - 4
Downstream speed = x + 4
∴ x + 4 = 3(x - 4) x + 4 = 3x - 12
∴ 2x = 16 ∴ x = 8 ..... Col. B > Col. A
t | \(20\frac{9}{11}\) |
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Solution
At 4 o'clock, the difference between hour and minute hand is 20 minutes i.e. minute hand lags the hour hand by 20 minutes. In 60 minutes, minute hand gains 55 minutes over hour hand.
∴ To gain 20 minutes over the hour hand, minute hand must actually show \(\frac{20\times 60}{55}=20\times \frac{12}{11}\)
=\(\frac{240}{11}=21\frac{9}{21}\) minutes past 4.
Col. A > Col. B
tonal duration of journey in houres | 20 |
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Solution
In 10 hours, lead taken by Lance = (13 - 8) × 10 = 50 km
New speed of Jonty = 16 kmph and that of Lance = 12 kmph
∴ Jonty has to cover 50 Ian with a relative speed of 4 kmph in \(\frac{50}{4}\) = 121⁄2 hours.
∴ Col.A = 10 + 121⁄2 = 221⁄2hours
The figure above consists of 4 squares and 6 rectangles. Areas of the 4 squares are as shown.
perimeter of the figure | 48 |
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Solution
Note that the sum of sides of the 4 squares = side of the big square.
∴ Length of square = 2 + 3 + 4 + 5 = 14
∴ Col A = 14 × 4 = 56 > Col. B
average arithmetic means of the 8 marked angles | 75° |
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Solution
Addition of all 4 triangles = 180 × 4 = 7200
Total of angles around the central point = 360° - 120° = 240°
∴ The average degree measure of 8 angles =\(\frac{480}{8}\)= 60
∴ Col. A < Col. B
The figure shows a circle with centre O.
20° ≤ x < 50°
Difference between Maximum and Minimum possible value of y° | 30 |
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Solution
Consider ΔOAB
OA = OB = radius
∴ ΔOAB is an isosceles triangle
∴ ∠OAB = ∠OBA = y°
Smallest possible value of x is 20°
∴ Largest possible value of y = 1⁄2(180 - 20) = 80°
Largest possible value of x = 50°
∴ Smallest possible value of y = 1⁄2(180- 50) = 65°
Range = Maximum Value - Minimum Value
∴ Col. A = 80 - 65 = 15° < Col. B
ΔABC is right angles at A. ΔXYZ is inscribed in ΔABC. AB = 3, AC = 4, BC = 5
Measure of angle P in degrees | 270° – (2m + 2n)° |
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Solution
Consider □ABZY
90 + m + 2n + m + p = 360°
∴ 2m + 2n + p = 270°
∴ p = 270°-(2m + 2n)°
∴ Col. A = Col. B
The figure below shows ΔABC and ΔMNT inside it.
p + q + r + s + x + y | 270° |
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Solution
Angles of a triangle add to 180°
Consider ΔMNT
∠m + ∠ + ∠t = 180°
i.e. 180 - (q + r)+ 180 - (s + x)+ 180 - (p + y) = 180°
∴ p + q + r s - s + x + y = 360°
The figure above represents a 16 em piece of string attached to the ends of an 8 em rod. String is now pulled so as to form the Slides of a triangle whose base is the rod.
The greatest possible area of such a triangle in cm2 | 20 |
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Solution
A triangle has maximum area when it is an equilateral triangle.
In this case, the side of the equilateral triangle formed measures 8 cm.
∴ Area = √3⁄4 × (8)2 = 16√3
Col.A = 16√3 = 16 × 1.732
Col.B = 20 = 16 × 1.25